1. Field of Invention
The present invention relates generally to a geospatial database access and query method, and more particularly to a map and Inertial Measurement Unit/Global Positioning System (IMU/GPS) navigation process. With the location information provided by an IMU/GPS integrated system, the geospatial database operations, such as database access and query, are sped up. With the map data from a geospatial database, the navigation performance and accuracy are enhanced. The present invention also supports real time mapping by using IMU/GPS integrated system as the positioning sensor.
2. Description of Related Arts
A geospatial database has a big volume of spatial and text data which are organized in a file system or in tabular fashion. The data is used by the user to query spatial information and associated features and text descriptions. Due to the amount of a geospatial database, there exists difficulty to efficiently perform database access and query.
The coordinate information is the basic element of a geospatial database. There is a need to incorporate coordinate information into the geospatial database access and query operations.
The Global Positioning System (GPS) is an all-weather, space based navigation system under development by the Department of Defense (DoD) to satisfy the requirements for the military forces to accurately determine their position, velocity, and time in a common reference system, anywhere on the Earth on a continuous basis. To provide a continuous global positioning capability, a scheme to orbit a sufficient number of GPS satellites to ensure that four were always electronically visible was developed. The GPS receiver is used to measure the distances to the satellites. Then the location expressed as latitude, longitude and elevation are derived.
The global positioning system receiver, which includes an antenna, a signal processing unit, and associated electronics, receives signals from the global positioning system satellites to obtain position, velocity, and time solution. The global positioning system principle of operation is based on range triangulation. Because the satellite position is known accurately via ephemeris data, the user can track the satellite""s transmitted signal and determine the signal propagation time. Since the signal travels at the speed of light, the user can calculate the geometrical range to the satellite. The actual range measurement (called the pseudorange) contains errors, for example, bias in the user""s clock relative to global positioning system reference time. Because atomic clocks are utilized in the satellites, their errors are much smaller in magnitude than the users"" clocks. Thus, for three-dimensional position determination, and also to calculate the cock bias, the pure global positioning system needs a minimum of four satellites to obtain the user""s location.
The position accuracy provided by a GPS receiver is roughly 100 meters when only Coarse/Acquisition (C/A) code is employed and the Selective Availability (SA) is on. For personal navigation this position accuracy need to be enhanced. To obtain enhanced navigation function and accuracy, other navigation data should be incorporated in the navigation process, such as a geospatial database.
An allowed patent application entitled xe2x80x9cEnhanced Global Positioning System and Map Navigation Processxe2x80x9d, application Ser. No. 09/546,349, invented by the same applicant of the present invention, Dr. Ching-Fang Lin, discloses a process of integrated GPS/Map database operation to facilitate the geospatial data query and to enhance navigation capability, but it still suffers the shortcoming of the blockage of GPS signals, thus the enhanced geospatial database operation and navigation couldn""t be achieved without a position from the GPS receiver.
There is a large demand for use of a map guidance system when driving and hiking. The shortfall of a map-only system is that it is unable to obtain the user""s current location and overlay it on the map. This system innovation and invention provides a method for map navigation enhanced by other positioning sensors, such as an inertial measurement unit/global positioning system (IMU/GPS) integrated system. The integrated IMU/GPS provides uninterrupted position information for the carrier, thus is superior than the GPS-only positioning system. There is a further demand for a portable system for mapping. Low-cost and high accuracy positioning sensors are required to obtain coordinates of definable features, such as streets, buildings, rivers, or even mountains. The precision IMU/GPS integrated system is the right solution for a low-cost map guidance system.
The main objective of the present invention is to provide an enhanced navigation process, which incorporates the GPS position data, IMU measurements, and geospatial map data.
Another objective of the present invention is to provide an efficient geospatial database query and access method by using GPS/IMU integrated position data in the geospatial data retrieval procedure.
Another objective of the present invention is to provide a time-space filtering method to fully fuse the GPS/IMU integrated position data and the geospatial map data to obtain enhanced navigation performance.
Another objective of the present invention is to provide a mechanism to incorporate the map data into the integration process of GPS and IMU measurements to improve the GPS/IMU navigation performance.